Fractal dimension and anisotropy of soil CO2 emission in a mechanically harvested sugarcane production area

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Anisotropy of track revelation in epidote: Results of a step etching experiment with Kr-86 ion tracks

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Topological signatures in CMB temperature anisotropy maps

We propose an alternative formalism to simulate cosmic microwave background (CMB) temperature maps in Lambda CDM universes with nontrivial spatial topologies. This formalism avoids the need to explicitly compute the eigenmodes of the Laplacian operator in the spatial sections. Instead, the covariance matrix of the coefficients of the spherical harmonic decomposition of the temperature anisotropies is expressed in terms of the elements of the covering group of the space. We obtain a decomposition of the correlation matrix that isolates the topological contribution to the CMB temperature anisotropies out of the simply connected contribution. A further decomposition of the topological signature of the correlation matrix for an arbitrary topology allows us to compute it in terms of correlation matrices corresponding to simpler topologies, for which closed quadrature formulas might be derived. We also use this decomposition to show that CMB temperature maps of (not too large) multiply connected universes must show patterns of alignment, and propose a method to look for these patterns, thus opening the door to the development of new methods for detecting the topology of our Universe even when the injectivity radius of space is slightly larger than the radius of the last scattering surface. We illustrate all these features with the simplest examples, those of flat homogeneous manifolds, i.e., tori, with special attention given to the cylinder, i.e., T-1 topology.

Upper-mantle seismic anisotropy from SKS splitting in the South American stable platform: A test of asthenospheric flow models beneath the lithosphere

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Temperature dependence and magnetocrystalline anisotropy studies of self-assembled L1(0)-Fe55Pt45 ferromagnetic nanocrystals

Temperature dependence and uniaxial magnetocrystalline anisotropy properties of the chemically synthesized 4 nm L1(0)-Fe55Pt45 nanoparticle assembly by a modified polyol route are reported. As-prepared nanoparticles are superparamagnetic presenting fcc structure, and annealing at 550 degrees C converts the assembly into ferromagnetic nanocrystals with large coercivity (H-C>1 T) in an L1(0) phase. Magnetic measurements showed an increasing in the ferromagnetically ordered fraction of the nanoparticles with the annealing temperature increases, and the remanence ratio, S=M-R/M-S congruent to 0.76, suggests an (111) textured film. A monotonic increase of the blocking temperature T-B, the uniaxial magnetocrystalline anisotropy constant K-U, and the coercivity H-C with increasing annealing temperature was observed. Magnetic parameters indicate an enhancement in the magnetic properties due to the improved Fe55Pt45 phase stabilizing, and the room-temperature stability parameter of 67, which indicates that the magnetization should be stable for more than ten years, makes this material suitable for ultrahigh-density magnetic recording application.(c) 2007 American Institute of Physics.

ANISOTROPY OF ELECTRICAL-PROPERTIES IN ALPHA-FE2O3 CERAMICS

Electrical conductivity and thermoelectric power measurements carried out in a heamatite ceramic showed a strong anisotropy in directions normal and parallel to the uniaxial pressing direction. This behaviour is similar to that verified in alpha-Fe2O3 single crystal. The results suggest that the extended structural defects, generated during sintering, disturb the magnetic order on the (001) planes of alpha-Fe2O3 and limit the mobility of n type carriers.

Anisotropy of the effective Lande factor in AlxGa1-x As parabolic quantum wells under applied magnetic fields

The anisotropy of the effective Lande factor in Al(x)Gal(1-x)As parabolic quantum wells under magnetic fields is theoretically investigated. The non-parabolicity and anisotropy of the conduction band are taken into account through the Ogg-McCombe Hamiltonian together with the cubic Dresselhaus spin-orbit term. The calculated effective g factor is larger when the magnetic field is applied along the growth direction. As the well widens, its anisotropy increases sharply and then decreases slowly. For the considered field strengths, the anisotropy is maximum for a well width similar to 50 angstrom. Moreover, this anisotropy increases with the field strength and the maximum value of the aluminum concentration within the quantum well. (C) 2010 Elsevier B.V. All rights reserved.

Fractal dimension and anisotropy of soil CO2 emission in an agricultural field during fallow

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Anisotropy of crystallite growth during sintering of SnO2 xerogels

The crytallite and pore-size evolution during isothermal sintering (400 ≤ T ≤ 700°C) of SnO2 xerogels was studied by X-ray line broadening and nitrogen adsorption-desorption isotherms. The experimental results show a strong anisotropy of crystallite growth between [110] and [101] directions. The preferential growth at [101] is followed by an increase in the mean pore size, reduction of the specific surface area and invariance of total pore volume. This behaviour is typical of grain coalescence sintering. The kinetic analysis of experimental results suggests that the crystallite coalescence at [101] is governed by lattice diffusion. The strong anisotropy of the growth causes pore-size distribution broadening, hindering the macroscopic shrinkage of the compact during sintering. © 1996 Chapman & Hall.

Anisotropy in the transport properties of type II superconducting films with periodic pinning

Using numerical simulations, we analyze the anisotropy effects in the critical currents and dynamical properties of vortices in a thin superconducting film submitted to hexagonal and Kagomé periodical pinning arrays. The calculations are performed at zero temperature, for transport currents parallel and perpendicular to the main axis of the lattice, and parallel to the diagonal axis of the rhombic unit cell. We show that the critical currents and dynamic properties are anisotropic for both pinning arrays and all directions of the transport current. The anisotropic effects are more significant just above the critical current and disappear with higher values of current and both pinning arrays. The dynamical phases for each case and a wide range of transport forces are analyzed. © 2012 Springer Science+Business Media, LLC.

Measurement of the elliptic anisotropy of charged particles produced in PbPb collisions at √sNN=2.76 TeV

The anisotropy of the azimuthal distributions of charged particles produced in √sNN=2.76 TeV PbPb collisions is studied with the CMS experiment at the LHC. The elliptic anisotropy parameter, v2, defined as the second coefficient in a Fourier expansion of the particle invariant yields, is extracted using the event-plane method, two- and four-particle cumulants, and Lee-Yang zeros. The anisotropy is presented as a function of transverse momentum (pT), pseudorapidity (η) over a broad kinematic range, 0.3anisotropy is found to obey a universal scaling with the transverse particle density for different collision systems and center-of-mass energies. © 2013 CERN. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Measurement of the azimuthal anisotropy of neutral pions in Pb-Pb collisions at √sNN=2.76 TeV

First measurements of the azimuthal anisotropy of neutral pions produced in Pb-Pb collisions at a center-of-mass energy of √sNN=2.76 TeV are presented. The amplitudes of the second Fourier component (v2) of the π0 azimuthal distributions are extracted using an event-plane technique. The values of v2 are studied as a function of the neutral pion transverse momentum (pT) for different classes of collision centrality in the kinematic range 1.6anisotropy results from √sNN=200 GeV Au-Au collisions at RHIC, despite a factor of ∼14 increase in the center-of-mass energy. In the momentum range 2.5

Effect of structural anisotropy on electrical and magnetic properties of polyaniline conducting films

It is shown that highly conducting films of polyaniline protonated with di-esters of sulfosuccinic and sulfophthalic acids which contain alkyl- or alkoxy-type substituents exhibit highly anisotropic structural, electrical and magnetic properties. The layered-like structure of these films can be described as consisting of polyaniline chains which are mainly oriented parallel to the plane of the film and form regular out-of-plane stacks. These stacks are separated by bilayers of the dopant anions. Accordingly, the main anisotropy observed for solution cast films implies in-plane and out-of-plane measurements. An electrical anisotropy of about 80 is found for the in-plane and out-of-plane electronic conductivities at 5 K. The temperature dependences of the in-plane and out-of-plane conductivities are qualitatively similar and have been fitted as a series combination of variable-range-hopping-type and power law contributions. A maximum is observed in the temperature dependence of the electrical anisotropy at low temperature. The films also show a clear anisotropy of magnetization whose temperature and field characteristics depend on the chemical structure of the dopant anion. © 2013 Elsevier B.V.

Iron oxides as proxies for characterizing anisotropy in soil CO2 emission in sugarcane areas under green harvest

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)